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#
# Author:: Richard Manyanza (<liseki@nyikacraftsmen.com>)
# Copyright:: Copyright 2014-2016, Richard Manyanza.
# License:: Apache License, Version 2.0
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#
require "chef/exceptions"
require "chef/platform/priority_map"
class Chef
#
# Provider Resolution
# ===================
#
# Provider resolution is the process of taking a Resource object and an
# action, and determining the Provider class that should be instantiated to
# handle the action.
#
# If the resource has its `provider` set, that is used.
#
# Otherwise, we take the lists of Providers that have registered as
# providing the DSL through `provides :dsl_name, <filters>` or
# `Chef.set_resource_priority_array :dsl_name, <filters>`. We filter each
# list of Providers through:
#
# 1. The filters it was registered with (such as `os: 'linux'` or
# `platform_family: 'debian'`)
# 2. `provides?(node, resource)`
# 3. `supports?(resource, action)`
#
# Anything that passes the filter and returns `true` to provides and supports,
# is considered a match. The first matching Provider in the *most recently
# registered list* is selected and returned.
#
class ProviderResolver
attr_reader :node
attr_reader :resource
attr_reader :action
def initialize(node, resource, action)
@node = node
@resource = resource
@action = action
end
def resolve
maybe_explicit_provider(resource) ||
maybe_custom_resource(resource) ||
maybe_dynamic_provider_resolution(resource, action) ||
raise(Chef::Exceptions::ProviderNotFound, "Cannot find a provider for #{resource} on #{node["platform"]} version #{node["platform_version"]}")
end
# Does NOT call provides? on the resource (it is assumed this is being
# called *from* provides?).
def provided_by?(provider_class)
potential_handlers.include?(provider_class)
end
def enabled_handlers
@enabled_handlers ||= potential_handlers.select { |handler| !overrode_provides?(handler) || handler.provides?(node, resource) }
end
# TODO deprecate this and allow actions to be passed as a filter to
# `provides` so we don't have to have two separate things.
# @api private
def supported_handlers
enabled_handlers.select { |handler| handler.supports?(resource, action) }
end
private
def potential_handlers
handler_map.list(node, resource.resource_name).uniq
end
# The list of handlers, with any in the priority_map moved to the front
def prioritized_handlers
@prioritized_handlers ||= begin
supported_handlers = self.supported_handlers
if supported_handlers.empty?
# We always require a provider to be able to call define_resource_requirements on. In the why-run case we need
# a provider to say "assuming /etc/init.d/whatever would have been installed" and in the non-why-run case we
# need to make a best guess at "cannot find /etc/init.d/whatever". We are essentially defining a "default" provider
# for the platform, which is the best we can do, but which might give misleading errors, but we cannot read minds.
Chef::Log.trace "No providers responded true to `supports?` for action #{action} on resource #{resource}, falling back to enabled handlers so we can return something anyway."
supported_handlers = enabled_handlers
end
prioritized = priority_map.list(node, resource.resource_name).flatten(1)
prioritized &= supported_handlers # Filter the priority map by the actual enabled handlers
prioritized |= supported_handlers # Bring back any handlers that aren't in the priority map, at the *end* (ordered set)
prioritized
end
end
# if its a custom resource, just grab the action class
def maybe_custom_resource(resource)
resource.class.action_class if resource.class.custom_resource?
end
# if resource.provider is set, just return one of those objects
def maybe_explicit_provider(resource)
resource.provider if resource.provider
end
# try dynamically finding a provider based on querying the providers to see what they support
def maybe_dynamic_provider_resolution(resource, action)
Chef::Log.trace "Providers for generic #{resource.resource_name} resource enabled on node include: #{enabled_handlers}"
handler = prioritized_handlers.first
if handler
Chef::Log.trace "Provider for action #{action} on resource #{resource} is #{handler}"
else
Chef::Log.trace "Dynamic provider resolver FAILED to resolve a provider for action #{action} on resource #{resource}"
end
handler
end
def priority_map
Chef.provider_priority_map
end
def handler_map
Chef.provider_handler_map
end
def overrode_provides?(handler)
handler.method(:provides?).owner != Chef::Provider.method(:provides?).owner
end
end
end
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